Photographic ligand for inducing disproportionation of silver {30 1 and processes of use thereof

ABSTRACT

Speed increase is obtained in photosensitive silver halide emulsions by disproportionation of Ag 1 associated with the latent image.

United States Patent Charkoudian July 8, 1975 PHOTOGRAPHIC LIGAND FOR INDUCING [58] Field Of Search 96/29 D, 29 R, 76 C, 76 R, DISPROPORTIONATION SILVER +1 96/77, 94 R, 95, 3, 65 AND PROCESSES OF USE THEREOF [75] Inventor: John C. Charkoudian, Cambridge, [56] J 1/ References cued Mass. UNlTED STATES PATENTS 3,415,644 12/1968 Land 96/3 [73] Ass'gnee :F Cmpmamn Cambndge 3,552,968 1/1971 Willems et al. 96/76 R 3,615,428 10/1971 Weed 915/76 R [22] Filed: June 3, 1974 Primary Examiner-David Klein [2]] Appl 475778 Attorney, Agent, or Firm-Philip G. Kiely Related US. Application Data [63] Continuation-impart of Ser. No. 327,797, Jan. 29, [57] ABSTRACT 1973 abandoned Speed increase is obtained in photosensitive silver hal- 52 us. 01 96/3; 96/29 R; 96/65; ide emulsions bydispmpomonation of Ag associ- 96/76 R; 96/77; 96/107 Int. Cl. G03c 7/00; G03c 5/54; G03c 1/48 ated with the latent image.

31 Claims, No Drawings PHOTOGRAPHIC LIGAND FOR INDUCING DISPROPORTIONATION OF SILVER +1 AND PROCESSES OF USE THEREOF CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 327,797 filed Jan. 29, 1973 now abandoned.

BACKGROUND OF THE INVENTION In the Oct. 4, 1972 issue of the Journal of the American Chemical Society, page 7189-7190, there is reported ligand-induced disproportionation of silver.

The article reports that contrary to a disproportion-' ation of copper and gold wherein the relatively high heat of hydration favors the disproportionation of the copper or gold" ions, the relatively low heat of hydration of Ag disfavors such a reaction, i.e., Ag is highly unstable. However, by employing a macrocyclic ligand which is relatively large and flat, the reaction of Ag and the ligand provides relatively high yields of Ag L and Ag wherein L is the ligand and the Ag is deposited as a mirror. The reaction may be carried out in water or methanol in which Ag is-soluble.

The stability of the complex is believed to be the result of the coordination of the Ag ion by the tetranitrogen macrocyclic ligand in an approximately square planar geometry. Thus, the stability of the high oxidation state of silver is believed to be the consequence of the four donor nitrogens being tightly bound to Ag in an approximately square planar'geornetry.

A novel photographic system has now been found employing the above-described disproportionation re action.

SUMMARY OF THE INVENTION Speed enhancement is achieved in photosensitive silver halide emulsions by the disproportionation of Ag in the vicinity of the latent image. Such disproportionation is preferably carried out by contacting the latent image with a macrocyclic ligand prior to development. Preferably, the ligand is disposed in the emulsion prior to exposure.

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a photosensitive element which includes a macrocyclic ligand capable of inducing disproportionation in Ag. By associating such a ligand with the exposed photosensitive silver halide emulsion layer, enhanced speed is achieved. In addition, substantially no fog is found in the photosensitive elements of the present invention.

The ligand is either disposed in the silver halide emulsion prior to exposure or is applied to the exposed emulsion prior to development. Thus, the action of the ligand on the latent image occurs before development.

A silver halide crystalconsists of positively charged silver ion (Ag) and negatively charged halide ions. A photon absorbed onto the crystal provides anelectron which combines with an Ag ion and reduces .it ,to a neutral silver atom (Ag As this process proceeds with a given quantity of photonsabsorbed, a small'sta ble cluster of reduced silver atomsh flatent image specks) are formed. These latentimage specks serve as catalytic centers for the reduction to silvje r'jo f silvieriionls in the exposed crystals by the ame o fl the' p graphic developer. This reduced 'mas's iofjsiil'vei'forms the image. The speed of a photographic system relates to the number of photonsincident on a crystal to providethe latent image specks capable of development. The fewer the photons required to produce Ag the greater, the speed.

While not intending to be bound by theory, it is believed that by contacting the'silver halide emulsion with the above-described ligand, the size of the latent image formed by exposure of the emulsion is increased, i.e., the speed is increased'Thus, the Ag ions in the vicinity of and onthe crystal .which are believed to be associated with the formation of the latent image are reacted with the ligand and then disproportionated to provide Ag which enlarges the latent image, and an Ag complex. The following general equation illustrates the described reaction: I

2Ag L 1 2 AgL Ag,

Thus, the presence of a macrocyclic ligand in the emulsion acts to rapidly produce Ag in the latent image upon exposure to a degree sufficient to build up the size of the latent image to produce a speed increase. The described macrocyclic ligand can be characterized as a sensitizer or latensification agent.

The ligand employed in the present invention is a non-aromatic macrocyclic ligand, i.e., long and flat, capable of stabilizing the Ag ion and which possesses four electron donor atoms, preferably containing four atoms capable of providing the described stabilizing effect to silver. Thus, the ligands suitable for use in the present invention may be represented by the formula:

wherein each X is a carbon chain of at least two carbon atoms.

Preferably, the ligand is a saturated or unsaturated macrocyclic Schiff base amine.

As examples of suitable ligands, mention may be made of the following:

,5 ,7, 1 2,1 2; 1 4-hexam ethyl- 1 ,4,8,1 hm aa zac clbietradecane (teta) v v 1 2 O 5,5, 7 ,-l2,14,14-hexamethyl-l,4,8,ll-tetraazacyclotet- C (CH radecaneltet'b) 1 1 v 3 2 The preparationof such ligands .is known to the art.

1 I r See, for example, J.A.C.S. 2644 (1964). H 1 The following non-limiting examples illustrate the c Y 2 1 T Z novel emulsions of the present invention.

H C- N I n----c i i EXAMPLEI CH 4 (Clrl l 3O Afilm unit was prepared by coating apolyester suppor't 'with' 5 O rr igsjft. of magenta dyedeveloper of the H2 o m a; v no-cn -cn 1 a I 1 7 9 I 3 H0-CH2-CH2 1 "'-'-C--CI?I2CH2 g H2 inabo11t l50'mgs/ft. of gelatin. Over the above- (CH described layer was coated a blue-sensitized silver 1 3 2\ 3 iodob'rornide 'emulsion containing 4 ing/g silver of t C c 7 Compound B ata coverage of about 85 mgs./ft; of sil- 2\ /H vei' and about 85 rngsJft. of gelatin. Over the emulsion C--- r g. layer was coated a' layer of gelatin at a coverage of D v 1 1 al aout' 3O mgs./ft. containing about 8 m'gsJft. of 2 2 '4,rneth'ylphenylhydi oquinone. The thus-formed negative was exposed through'a step wedge to selectively C---N H T H \H filtered radiation and then processed :by contacting the 2 C C 2 negative with a processing composition while in superposition with an image-receiving element in the dark C 2 for '10 'minutes. The image-receiving element comprised a 4 mil polyethylene terephthalate film base hav- H ing coated thereon the following layers:

1. the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high viscosity poly-(ethylene/maleic anhydride). 140 grams of n-butyl alcohol and 1 cc. of 85% phosphoric acid to provide a polymeric acid layer approximately 0.75 mil thick;

2. a aqueous emulsion of a diacetone acrylamide/acrylamide copolymer grafted onto a polyvinyl alcohol backbone to provide an inert spacer layer approximately 0.3 mil thick; and

3. A 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of approximately 600 mgs/ftf. to provide a polymeric image-receiving layer approximately 0.40 mil thick. The processing composition comprised the following:

Water The film unit of the present invention, compared with a film unit prepared and processed as above except that no macrocyclic ligand was disposed therein, showed a speed enhancement of about one step.

The silver halide emulsions of the present invention are suitable for employment in both color and black and white photographic systems.

The present invention is particularly useful in black and white silver transfer processes.

Diffusion transfer processes are now quite well known and their details need not be repeated here. In a silver transfer process, for example, a photoexposed silver halide material and a silver precipitating material are subjected to an aqueous alkaline solution comprising at least a silver halide developing agent and a silver halide solvent. The developing agent reduces exposed silver halide to silver and the solvent reacts with unreduced silver halide to form a complex silver salt that migrates to the silver precipitating material where it is precipitated or reduced to form a visible silver image.

At the completion of the process the two strata may be separated in order to render the positive print visible. Alternatively, in accordance with the teachings of US. Pat. No. 2,861,885, the two strata need not be separated in order to render the positive print visible.

EXAMPLE I] A film unit was prepared by coating a polyester support with mgs./ft. of yellow dye developer of the formula:

in about mgs/ft. of gelatin. Over the abovedescribed layer was coated a blue-sensitized silver iodobromide emulsion containing 4 mg./g. silver of Compound B ata coverage of about mgs./ft. of silver and about 85 mgs./ft. of gelatin. Over the emulsion layer was coated a layerof gelatin at a coverage of about 30 mgs./ft. containing about 8 mgs./ft. of 4'-methylphenylhydroquinone. The thus-formed negative was exposed and processed as in Example 1. The image-receiving element employed was the same as that used in Example I. The processing composition comprised:

Water cc. Potassium hydroxide 10.6 g. Lithium hydroxide monohydride 0.45 g. Titanium dioxide I 95.8 g. Carboxymethyl cellulose sodium salt 1.84 g. B'enzotriazole 1.27 g. 5-bromo-6-methy1-4- azabenzimidazole .064 g. N-phenelhyl-wpicolinium bromide 1.65 g. G-methyl uracil 0.67 g. Lithium nitrate E. 0.22 g. N-Z-hydroxyethyl-N.N',N'-triscarboxmethyl diamine tetraacetic acid 1.9 g. Bis(-aminoethyl)-sulfide 0.05 g. Carbowax (Polyethylene glycol,

M.W. 6000) 1.23 g Silica SiO i 1.67 g N-benzyl-a-picolinium bromide 2.86 g fi-benzylaminopurine 0.62 g

OH I

--COOH H O 2 n 1s 37 EXAMPLE Ill 15 Wulcr 100 cc. Potassium hydroxide l0.5 g. I Lithium hydroxide monohydride 0.45 g. A film umt was prepared by coating a polyester supg g z l 953 8- port with 50 mgs./ft. of cyan dye developer of the forg' f f jflf y Cc u 23] g mula: Bcnzotriazole L27 r HC--NH.--O S l 2 CH2 CH3 N=C C----N l H \M H o -mr-err C HO l CH Y cu 2 T 3 l C OH I ll ap mr o s fi N H CH CH 3 SO -NHCH 2 on I CH H 2 in about 75 mgsjft. of gelatin. Over the aboveqy d d l d bl d azabenzimidazole .064

escrr e ayer was coate a ue-sensmze s1 ver N phencthyl a plcohmum iodobromide emulsion containing 4 mg./g silver of 45 bromide L65 2 o-methyl uracil 0.67 Compound B at a coverage of about 150 mgs./ft. of Sll- Lithium nitrate 012 ver and about 150 mgs./ft. of gelatin. Over the emul- S l' boxmethyl dramme slon layer was coated a layer of gelatm at a coverage of temmcetic acid 19 about 30 mgs./ft. The thus-formed negative was ex- BiS(-aminOeIhyl)-Sulfide Q05 posed and processed as in Example I above. The image- 50 926%? (Polyethylene glycol receiving element employed was the same as that em- Silica v 1.67 ployed in Example I. The processing composition comg f i g 2 86 prised: o-benzylarninopurinc 0.62

C H SO NH N N 16 33 2" H H coon EXAMPLE IV A film unit was prepared by coating a polyester support with 50 mgs./ft. of hydroquinone in 50 mgs./ft.'*- of gelatin. Over the described layer was coated a bluesensitive silver iodobromide emulsion containing 4 mg./g of sliver of Compound 8, at a coverage of about 150 mgs/ft. of silver and 150 mgs/ft. of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. and a layer of succinaldehyde at a coverage of about ll.5 rugs/ft The thus=formed negative was exposed through a step wedge to selectively filtered radiation and then processed by contacting the negative for six minutes in the dark with a processing composition while in superposi= tion with a polyester cover sheet. The processing com= position comprised the following:

Water Potassium hydroxide Qeslum hydroxide Titanium dioxide Carboxyrnethyl cellulose Benizotriazole 5=hromo=o=mcthyl=4= azubenzimidazole 2=methylimida2ole N=phenethyl=a=picolinium bromide At the end of that time, the development was stopped by washing the negative with acetic acid: Compared to a control iilm unit prepared and processed in the same manner except that the control did not contain Com= pound B, the film unit of this invention showed about one stop increase in speed.

EXAMPLE V The procedure of Example I was repeated except that the emulsion contained no ligand and the exposed emulsion was contacted with a methanol solution ofthe ligand prior to exposure Approximately one stop speed gicrcaso was noted over a control as well as a lower Employing silver halide emulsion of the present in= .vention will provide enhanced speed in such systems by providing a greater quantity of reduced silver per pho= ton of exposure than would be obtained in an emulsion which was not contacted with the macrocyclic ligand,

Additive color photography involves the exposure of a photosensitive silver halide stratum through an opti: cal screen element or rcssau which possesses filter or screen elements selectively transmitting predetermined portions of the electromagnetic radiation incident on said screen. Processing of the thus=caposcd silver hal: ids stratum results in the deposit of silver as a function of the degree of exposure behind specific segments of the filter elements to modulate the quantity of light passing through the given screen elements during projection of the thus-recorded image.

ln additive color screen units, the photoresponsive material and the color screen may comprise separate and distinct elements appropriately registered during exposure and during viewing or projection of the im age. Thus, subsequent to initial exposure of the photoresponsive material, the screen may be removed to permit processing and formation of the silver image, and then recombined with the thus-formed silver image for viewing of the finished image. it is preferred, however, to permanently position the additive color screen and the photoresponsive material together. in such permanent arrangement, it is, of course, necessary to insulate the screen by, for example, barrier elements or intermediate layers, to protect the screen from degradation or change by the action of the processing composition applied to the photoresponsive material to develop the image recorded therein.

Generally, suitable film assemblages comprise a pan= chromaticaiiy sensitized silver halide stratum and a multicolor additive color screen, As examples of such structures, reference may be had to the Dufay film units and those of Bacon DuHauron. A variety of con= ventional photosensitive layers may be employed in ad= ditive film units depending upon the specific type of processing to be employed. For example, depending upon the specific photosensitive layer selected, a direct negative image and a direct positive image may be formed by reversal techniques, a direct image by the employment ofa conventional direct positive emulsion; by silver diffusion transfer processing or by the forma= tion in a separate layer or a separate positive image which is then placed in registration with the same screen used for exposure of the film unit, or with a sub= stantially identical screen,

A preferred iiirn unit employs an image=receiving component intermediate the photosensitive silver hal= ide stratum and the additive multicolor screen. in such a film unit, exposure of the silver halide emulsion is ac= complishcd through the screen unit and the image= receiving component. Subsequent processing results in the formation of a positive silver image in the imagc= receiving component nest adjacent the additive multi= color screen, The aiorementioned film unit is one are ample of a structure which obviates registration prob= lerns since the screen employed for citposing is in auto= matic registration with the positive silver image for viewing; in the aforementioned film unit, the silver hal= ids stratum may be removed or allowed to remain in position subsequent to formation of the positive silver image.

As examples of suitable film structures which comprise negative and positive images in superposition and formed by diffusion transfer reversal processes, mention may be made of U.S. Pat. Nos. 2,86l,885; 2,726,154; 2,944,894; 3,536,488; and also U.S. Pat. Nos. 3,615,427; 3,615,428; 3,615,429 and 3,615,426.

The utility of such film units wherein the silver halide layer remains an integral portion of the film unit subsequent to positive image formation is achieved by employing as the image-receiving element a layer which provides an unusually effective silver precipitating environment which causes the silver deposited therein to possess an extraordinarily high covering power in comparison with negative silver developed in the silver halide layer. For greater discussion of such a phenomenon, see Edwin H. Land, One Step Photography, Photographic Journal, Section A, pages 7 to 15, January, 1950.

The above-mentioned integral film unit applications are particularly desirable for employment as cine film for motion picture projection, for example, such as the cine film system described in U.S. Pat No. 3,615,427 issued Oct. 26, 1971. Processing of such film units, as well as the specific composition of the processing composition, is detailed in the aforementioned patents and applications.

Various diffusion transfer systems for forming color images have heretofore been disclosed in the art. Gen erally speaking, such systems rely for color image formation upon a differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more diffusible and which is therefore selectively transferred, at least in part, by dif= fusion, to a superposed dyeable stratum to impart thereto the desired color transfer image, The differen= tial in mobility or solubility may for example be db 7 tained'by a chemical action such as a redox reaction or a coupling reaction.

The dye image=providing materials which may be em= played in such processes generally may be character= ized as either (I) initially soluble or diffusible in the processing composition but are selectively rendered non=diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non=diffusible in the processing composition but which are selectively rendered difrusible in an imagewise pattern as a func= tion of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.

As examples ofinitlally soluble or diffusible materials and their application in color diffusion transfer, men= tion may be made of those disclosed, for example, in

US, Pat. Nos. 2,647,049; 2,6613%: 2,638,244:

2,698,798; 2,802,735; 2,77 't,668; and 2,933,606, As examples of initially non=diffusible materials and their use in color transfer systems, mention be made of the materials and systems disclosed in US Pat. Nos, 3 143939; 3,443,940: 3,327,550; 3537,55 3,227,552; 3,227,554t 3,243,294 and 3445233,

in any of these systems, multicolor ob= tamed by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image=providing material exhibiting desired spectral absorption characteristics, The most commonly employed elements of this type are the so'called tripack structures employing a blue, a greenand a red-sensitive silver halide layer having associated therewith, respectively, a yellow, 21 magenta and a cyan dye image-providing material.

A particularly useful system for forming color images by diffusion transfer is that described in U.S. Pat. No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the dye imageproviding materials. U.S. Pat. No. 2,983,606 is incorporated herein in its entirety.

In color diffusion transfer systems of the foregoing description, color images are obtained by exposing a photosensitive element or negative component" comprising at least a light-sensitive layer, e.g., a gelatino silver halide emulsion layer, having a dye imageproviding material associated therewith in the same or in an adjacent layer, to form a developable image; developing this exposed element with a processing composition to form an imagewise distribution of a soluble and diffusible image-providing material; and transferring this imagewise distribution, at least in part, by dif fusion, to a superposed receiving element or positive component" comprising at least a dyeable stratum to impart to this stratum a color transfer image. The negative and positive components may be separate elements which are brought together during processing and thereafter either retained together as the final print or separated following image formation; or they may together comprise a unitary structure, e.g., integral negativepositive film units wherein the negative and posi= tive components are laminated and/or otherwise physi= cally retained together at least prior to image forma= tion.

While the present invention is applicable both to those systems wherein the dyeable stratum is contained on a separate element and to those systems wherein the dyeable stratum and the photosensitive strata comprise a unitary structure, of particular interest are those inte= gral negative=positive film units adapted for forming color transfer images viewable without separation, to, wherein the positive component need not be separated from the negative component for view purposes. As examples of such integral negative=positive film units,

mention may be made of those described and claimed in Pat, Nos. sates 4a; gall 5,645; 3,415,646; 3473,1925; 3,373,043: 3,576,625; 3,573,023 3,534,164 and 3,25%,165.

The specific composition or method of preparation of silver halide emulsions suitable foruso in the present invention is not critical to the operation of the present invention, For example, emulsions ofthe preent mven: tion may be employed in emulsions for wet preessing, emulsions employed in diffusion transfer processing and direct positive emulsions conventional spe tral and chemical sonsitiiers be employed well at additives such as coating aids, hardeners, vis j increasing agents, stabiiiners, preservatives, and

ride, silver iodide, silver bromide, muted 'si lides silver ehlo bromide, s1 yer oh roiodo: bromidaor s lver iodooro" (e, or varying halide ratios and varying silver What is claimed is: i, A photosensr've silvea non-aromatic macrocyclic ligand having four electron donor atoms of the formula:

5. A product as defined in claim 1 wherein said ligand 20 is:

6. A product as defined in claim 1 wherein said ligand 9. A product as defined in claim 1 wherein said silver halide emulsion iscarried on a support.

10. A photographic silver diffusion transfer film unit which comprises photosensitive silver halide, silver precipitating nuclei and associated with said silver halide, a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:

wherein X is a carbon chain of at least two carbon atoms.

11. A product as defined in claim 10 wherein said film unit includes a common support carrying a layer comprising silver precipitating nuclei and a layer comprising silver halide crystals. v

12. A product as defined in claim 11 wherein said film unit is a permanent laminate.

13. A product as defined in claim 11 wherein said common support is transparent.

14. A photographic silver diffusion transfer film unit as defined in claim 13 which includes an additive color screen intermediate said transparent common support and next adjacent essential layer.

15. A photographic silver diffusion transfer film unit which comprises a plurality of layers including a photosensitive layer containing photosensitive silver halide and at least one substantially photoinsensitive layer, at least one photoinsensitive layer containing a silver precipitating agent and at least one photoinsensitive layer including a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:

wherein X is a carbon chain of at least two carbon atoms.

16. A product as defined in claim wherein said photosensitive layer containing said silver halide and said photoinsensitive layer containing said silver precipitating agent are carried on separate supports.

17. A product as defined in claim 10 which includes an additive color screen.

18. In a photosensitive element including at least one light-sensitive silver halide layer wherein each of which has a dye image-providing material associated therewith, the improvement which comprises including in at least one silver halide layer a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:

wherein each X is a carbon chain of at least two carbon atoms.

19. An element as defined in claim 18 which includes a red-sensitive gelatino silver halide emulsion having a cyan dye image-providing material associated therewith; a green-sensitive gelatino silver halide emulsion having a magenta dye image-providing material associated therewith; and a blue-sensitive gelatino silver halide emulsion having a yellow dye image-providing material associated therewith.

20. An element as defined in claim 18 which includes a positive component including at least a dyeable stratum.

21. A photographic film unit which comprises, in

combination:

a photosensitive element having a diffusion transfer image-receiving element affixed at least one edge thereof, said photosensitive element comprising a support carrying:

a. a red-sensitive silver halide emulsion having associated therewith a cyan dye developer;

b. a green-sensitive silver halide emulsion having associated therewith a magenta dye developer;

c. a blue-sensitive silver halide emulsion having associated therewith a yellow dye developer; at least one of said silver halide emulsions having disposed 16 therein a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:

//X\\ I N: :N x X wherein each X is a carbon chain of at least two carbon atoms;

said diffusion transfer image-receiving element comprising a support layer carrying:

an alkaline processing composition permeable and dyeable layer wherein said photosensitive and said image-receiving elements are adapted to be superposed, the support layers of each comprising the extremities of the superposed structure.

22. The product as defined in claim 21 wherein said non-aromatic macrocyclic ligand is disposed in each of said silver halide emulsion layers.

23. The product as defined in claim 21 including a rupturable container retaining an aqueous alkaline processing composition affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said superposed photosensitive and said imagereceiving elements.

24. The product as defined in claim 23 wherein said image-receiving element support layer is transparent.

25. The product as defined in claim 22 wherein said photographic film unit comprises a composite structure comprising said photosensitive element and said imagereceiving element permanently affixed each to the other in superposed relationship, the support layers of each of said elements comprising the extremities of said composite structure.

26. A photographic process which comprises developing an exposed photosensitive element comprising an exposed silver halide emulsion containing a nonaromatic macrocyclic ligand having four electron donor atoms of the formula:

wherein each X is a carbon chain of at least two carbon atoms; and

b. contacting said exposed film unit with a processing composition containing a silver halide developing agent and a silver halide solvent. thereby providing a visible diffusion transfer process silver image to said unit. as a function of the point-to-point degree of exposure thereof.

28. A silver diffusion transfer photographic process which comprises, in combination, the steps of:

a. exposing a film unit which comprises a permanent laminate which includes a support carrying on one surface a layer comprising silver precipitating nuclei and a layer comprising photosensitive silver halide having associated therewith a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:

wherein each X is a carbon chain of at least two carbon atoms; and b. contacting said exposed film unit with a processing composition containing a silver halide developing agent and a silver halide solvent, thereby providing a visible diffusion transfer process silver image to said unit, as a function of the point-to-point degree of exposure thereof.

29. A diffusion transfer color photographic process as defined in claim 27 wherein said film unit includes a color screen and exposure of said film unit is accomplished by radiation transmitted through said screen.

30. A diffusion transfer multicolor photographic process as defined in claim 29 wherein said color screen comprises a trichromatic additive color screen comprising red, green and blue optical filter elements in a screen pattern.

31. A process which comprises exposing a photosensitive silver halide emulsion, contacting said exposed emulsion with a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:

wherein each X is a carbon chain of at least two carbon atoms; and developing said emulsion. 

1. A photosensitive silver halide emulsion comprising a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:
 2. A product as defined in claim 1 wherein the emulsion includes spectral sensitizing agents.
 3. A product as defined in claim 1 wherein said emulsion includes chemical sensitizing agents.
 4. A product as defined in claim 1 wherein said emulsion contains an antifoggant.
 5. A product as defined in claim 1 wherein said ligand is:
 6. A product as defined in claim 1 wherein said ligand is:
 7. A product as defined in claim 1 wherein said ligand is:
 8. A product as defined in claim 1 wherein said ligand is:
 9. A product as defined in claim 1 wherein said silver halide emulsion is carried on a support.
 10. A photographic silver diffusion transfer film unit which comprises photosensitive silver halide, silver precipitating nuclei and associated with said silver halide, a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:
 11. A product as defined in claim 10 wherein said film unit includes a common support carrying a layer comprising silver precipitating nuclei and a layer comprising silver halide crystals.
 12. A product as defined in claim 11 wherein said film unit is a permanent laminate.
 13. A product as defined in claim 11 wherein said common support is transparent.
 14. A photographic silver diffusion transfer film unit as defined in claim 13 which includes an additive color screen intermediate said transparent common support and next adjacent essential layer.
 15. A photographic silver diffusion transfer film unit which comprises a plurality of layers including a photosensitive layer containing photosensitive silver halide and at least one substantially photoinsensitive layer, at least one photoinsensitive layer containing a silver precipitating agent and at least one photoinsensitive layer including a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:
 16. A product as defined in claim 15 wherein said photosensitive layer containing said silver halide and said photoinsensitive layer containing said silver precipitating agent are carried on separate supports.
 17. A product as defined in claim 10 which includes an additive color screen.
 18. In a photosensitive element including at least one light-sensitive silver halide layer wherein each of which has a dye image-providing material associated therewith, the improvement which comprises including in at least one silver halide layer a non-aromatic macrocyclic ligand having four electron donor atoms of the formulA:
 19. An element as defined in claim 18 which includes a red-sensitive gelatino silver halide emulsion having a cyan dye image-providing material associated therewith; a green-sensitive gelatino silver halide emulsion having a magenta dye image-providing material associated therewith; and a blue-sensitive gelatino silver halide emulsion having a yellow dye image-providing material associated therewith.
 20. An element as defined in claim 18 which includes a positive component including at least a dyeable stratum.
 21. A photographic film unit which comprises, in combination: a photosensitive element having a diffusion transfer image-receiving element affixed at least one edge thereof, said photosensitive element comprising a support carrying: a. a red-sensitive silver halide emulsion having associated therewith a cyan dye developer; b. a green-sensitive silver halide emulsion having associated therewith a magenta dye developer; c. a blue-sensitive silver halide emulsion having associated therewith a yellow dye developer; at least one of said silver halide emulsions having disposed therein a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:
 22. The product as defined in claim 21 wherein said non-aromatic macrocyclic ligand is disposed in each of said silver halide emulsion layers.
 23. The product as defined in claim 21 including a rupturable container retaining an aqueous alkaline processing composition affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said superposed photosensitive and said image-receiving elements.
 24. The product as defined in claim 23 wherein said image-receiving element support layer is transparent.
 25. The product as defined in claim 22 wherein said photographic film unit comprises a composite structure comprising said photosensitive element and said image-receiving element permanently affixed each to the other in superposed relationship, the support layers of each of said elements comprising the extremities of said composite structure.
 26. A photographic process which comprises developing an exposed photosensitive element comprising an exposed silver halide emulsion containing a non-aromatic macrocyclic ligand having four electron donor atoms of the formula:
 27. A SILVER DIFFUSION TRANSFER PHOTOGRAPHIC PROCESS WHICH COMPRISES, IN COMBINATION, THE STEPS OF: A. EXPOSING A PHOTOGRAPHIC FILM UNIT COMPRISING PHOTOSENSITIVE SILVER HALIDE AND SILVER PRECIPITATING NUCLEI WHEREIN SAID SILVER HALIDE HAS ASSOCIATED THEREWITH A NON-AROMATIC MACROCYCLIC LIGAND HAVING FOUR ELECTRON DONOR ATOMS OF THE FORMULA:
 28. A silver diffusion transfer photographic process which comprises, in combination, the steps of: a. exposing a film unit which comprises a permanent laminate which includes a support carrying on one surface a layer comprising silver precipitating nuclei and a layer comprising photosensitive silver halide having associated therewith a non-aromatic macrocycLic ligand having four electron donor atoms of the formula:
 29. A DIFFUSION TRANSFER COLOR PHOTOGRAPHIC PROCESS AS DEFINED IN CLAIM 27 WHEREIN SAID FILM UNIT INCLUDES A COLOR SCREEN AND EXPOSURE OF SAID FILM UNIT IS ACCOMPLISHED BY RADIATION TRANSMITTED THROUGH SAID SCREEN.
 30. A diffusion transfer multicolor photographic process as defined in claim 29 wherein said color screen comprises a trichromatic additive color screen comprising red, green and blue optical filter elements in a screen pattern.
 31. A process which comprises exposing a photosensitive silver halide emulsion, contacting said exposed emulsion with a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: 